A. Field of the Invention
This invention relates to valves and more particularly to valves for mud pumps.
B. Description of the Prior Art
During the drilling of oil and gas wells, drilling fluids are circulated within the bore hole by means of positive displacement pumps commonly called mud pumps. The inlet and outlet ports of mud pumps are provided with poppet type valves, which include a seat ring and a valve disc adapted for reciprocal motion with respect to the seat ring. The disc also includes an elastomer insert snap fitted into a groove around the periphere of the disc. The disc also includes a unitary upper and lower guide stem.
The life of mud pump valves is limited by the life of the insert. In prior art valves, the groove is of a circular cross section or includes a round bottom. The insert is conformed to fit to the contours of the groove and is normally in the shape of an O-ring. During opening and closing of the valve, these O-ring inserts are subject to twisting, which causes fatigue and eventual destruction of the ring. Also, abrasive solids become trapped between the groove and the insert, further shortening the life of the insert. Additionally, as the insert is compressed upon closure of the valve, portions of the insert are extruded beyond the limits of the groove causing an additional area of fatigue. A further shortcoming of the heretofore existing valves is in the unitary construction of the valve disc and stems. It is expensive to fabricate such structures. Moreover, different mud pumps have different dimensions, which require valves with stems of different lengths and diameters.